Fire resistant hydraulic fluid



United States Patent 3,236,778 FIRE RESISTANT HYDRAULIC FLUID Herbert A. McIntosh, Groves, Tex., assignor to Texaco Inc, New York, N.Y., a corporation of Delaware N0 Drawing. Filed May 29, 1962, Ser. No. 198,438 3 Claims. (Cl. 252-78) This invention relates to a fire resistant hydraulic fluid. More particularly, it concerns a water-in-oil emulsion having a specific composition rendering it excellent for use in the process of transmitting power without danger of fire. Specifically, this invention is an improvement in the emulsion stability of fire resistant hydraulic fiuids described and claimed in US. Patent 2,965,574, which issued to Raymond B. Tierney, Richard K. Meyers and Robert H. Krug on December 20, 1960.

In recent years the increased emphasis on industrial safety programs has resulted in a growing awareness on the part of industry that large volumes of mineral hydraulic oils in exposed areas constitute a dangerous safety hazard with respect to fires and explosions. A number of different soultions to the problem have been considered. These consisted of the use of various types of compositions which were intended to duplicate the performance of a mineral oil hydraulic fluid without the accompanying fire hazard. In commonly assigned US. Patent 2,965,574 there are disclosed water-in-oil emulsion lubricants which are outstanding in meeting these requirements. The emulsion hydraulic fluids of this patent duplicate mineral oil performance in the process of transmitting power Without fire hazard and are not subject to the objection raised against prior art products.

The compositions of U.S. Patent 2,965,574 comprise from 60 to 40 volume percent of water in the internal phase and from 40 to 60 volume percent of an oleaginous blend containing a major portion of mineral oil having an upper viscosity limit of 300 SUS at 100 F. in the external phase, an emulsifying agent stelected from the group consisting of fatty acid partial esters of six carbon polyhydric alcohol monoand dianhydrides, in combination with no more than 20 precent, based on the emulsifying agent, of hydrophilic polyoxyalkylene derivatives of C to C fatty acid partial esters of six carbon polyhydric alcohol monoand dianhydrides.

The compositions of the present invention differ from that of US. Patent 2,965,574 in the nature of the hydrophilic emulsifying agent. The present invention replaces the polyoxyalkylene derivatives of fatty acid partial esters with ethylene oxide adducts of C to C alkylphenols wherein there are 10 to 40 mols of ethylene oxide per mol of alkyl phenyl, preferably C C alkylphenols with 30-35 mols of ethylene oxide. The use of the prescribed ethylene oxide adduct of alkylphenol as the hydrophilic emulsifying agent imparts to the compositions of the present invention exceptional and unexpected thermal stability.

The improved fire resistant hydraulic fluid of this invention is a water-in-oil emulsion comprising from 60 to 40 volume percent of Water in the internal phase and from 40 to 60 percent of an oleaginous blend containing a major portion of a paraflin of naphthene base mineral oil having a viscosity range of about 50-300 SUS at 100 F. in the external phase, 1 to about 12 volume percent of a lipophilic emulsifying agent selecte from the group consisting of fatty acid partial esters of six carbon polyhydric alcohol monoand dianhydrides and mixtures thereof, and 0.05 to 2.50 volume percent, which is equivalent to to 20 volume percent based on the lipophilic emulsifying agent of a specific hydrophilic emulsifying agent, namely, an ethylene oxide-C to C alkylphenol adduct containing 10 to 40 mols of ethylene oxide per mol of alkylphenol.

It is important that no more than 20 volume percent or less than5 volume percent of the hydrophilic emulsifying agent based on the lipophilic emulsifying agent be used. The range of 5 to 20 volume percent based on the lipophilic emulsifying agent for the hydrophilic emulsifying agent is critical because an amount in excess of this range causes formation of an oil-in-water emulsion, which does not have sulficient lubricating properties to meet the requirements of an improved fire resistant hydraulic fluid. An amount of less than this range would form an unacceptable unstable emulsion.

A volatile corrosion inhibitor in an amount sufiicient to inhibit corrosion by the emulsion while the emulsion is in the vapor and liquid phases is usually added to the blend. Preferably, in order to meet the performance standard of inhibited mineral oil hydraulic fluids, the emulsion may further contain a minor amount of an antiwear agent and a minor amount of an antioxidant for the oil phase of the emulsion. In addition, an antifoam agent and a pour point depressant have also been found to be extremely useful.

Any type of mineral oil, paraflin base or naphthene base or mixture thereof, is useful in accordance with this invention as long as the viscosity of the oil is in the range of 50 to 300 SUS at F. The preferred mineral oil is a paraffin or naphthene base oil or mixtures thereof having a viscosity of from 50 to 100 SUS at 100 F., a flash point ranging from 300 to 375 F., and a pour point of not more than +20 F. Since at least 40 volume percent of water is required to render the emulsion fire resistant, the oil component, of necessity, must meet a low viscosity requirement, so that when mixed with water the resulting fluid is not excessively viscous, thus preventing its usefulness as a hydraulic fluid.

The preparation of a water-in-oil emulsion with the concentration of water useful in accordance with this invention without experiencing an emulsion reversal and maintaining emulsion stability had been a problem. However, with the emulsifying agents of the present invention, this problem has been solved.

Examples of the lipophilic emulsifying agents utilized in the present invention include the partial esters of sorbitan, sorbide, mannitan, mannide, dulcitan and dulcide. These compounds, per se, and the method of producting them are set forth in US. Patent, 2,322,820 and 2,322,821.

The hydrophilic emulsifying agents which constitute the improvement of the present invention have the general wherein R is an alkyl group containing 4 to 24 carbon atoms and n has a value of 10 to 40. Examples of these hydrophilic emulsifying agents include adducts of 10 mols ethylene oxide with one mol of octylphenol, 10 mols of ethylene oxide with one mol of nonylphenol, 14 mols of ethylene oxide with one mol of 2-ethylhexylphenol, 16 mols of ethylene oxide with one mol of nonylphenol, 20 mols of ethylene oxide with one mol of octadecylphenol, 24 mols of ethylene oxide with one mol of octylphenol, 36 mols of ethylene oxide with one mol of nonylphenol, and 40 mols of ethylene oxide with one mol of nonlyphenol.

Table I shows the compositions of this invention in comparison with the composition disclosed and claimed in afore-identified commonly assigned patent and Table II shows the results of the thermal stability tests on these compositions.

TABLE I A, vol B, vol. 0, vol. D, vol. percent percent percent percent N aplithene base mineral oil having an SUS viscosity at 100 F. of75 96. 40 83. 94 Parafiin base mineral oil having an SUS viscosity at 100 I of 75 92.51 23.32 Naphthene base mineral oil having an SUS viscosity at 100 F. ofS 9. 33 Parailin base mineral oil having an SUS viscosity at 100 F. of 105 69.95 Polyoxyethylene sorbitian monolaurate 1. 23 Sorbitan monooleate 5. 56 2. 69 5. 50 5.56 Ethylene oxide nonylphenol adduct 301molratioin a 60% active water solution 0.28 0. 54 0. 54 4,methyl,2,G-ditertiary butylphenoL. 0. 30 0. 28 0.28 0. 28 2,hydroxypropylamine nitrite 0. 40 0. 35 0. 35 0.35 kerosene solution of 1,000 centistoke dimethylsilicone polymer, p.p.m 150 150 150 150 Finished emulsion (vol. percent):

Bose blend. 50 60 55 60 Water 50 40 45 40 TAB LE IL-THE RMAL STABILITY TEST Room Temp. 150 F. Emulsion Results After One Month 25% cream compllete separation within 1 Fail.

wee 2% oil 20% oil Pass. cream 25% oil..." Pass. 2% oil 45% oil Pass.

In the above Tables I and II Emulsion A was the emulsion disclosed and claimed in US. Patent 2,965,574. Emulsion stability was compared by measuring separations occurring when the emulsion were stored at 150 F. and room temperature.

It is seen from the foregoing Table II that the emulsion compositions of the present invention demonstrate excellent thermal stability compared to the emulsion disclosed in US. Patent 2,965,574.

In further evaluating the stability of the emulsions of the present invention, a test generally referred to as the Modified Vickers Pump Test was employed. The apparatus used in this test is described in US. Patent 2,965,574.

The Modified Vickers Pump Test procedure consists of charging the Vickers Pump System with three gallons of testfluid and running at a temperature of about 150 F. Samples were periodically withdrawn from the reservoir to observe emulsion stability. The emulsions evaluated in the Modified Vickers Pump Test were the same as those disclosed in Table I above. The results of the Modified Vickers Pump Test are summarized in Table III below.

TABLE III.STABILITY OF EMULSIONS IN MODIFIED UMP TEST Emulsions A B O D Hours or continuous operation over which emulsion was stable 200 800 940 830 carbonate content showed slightly less emulsion stability on storage, however, they were nonetheless adjudged to be satisfactory for use in hydraulic systems.

Owing to the large amount of water present in the emulsion, it was found desirable but not necessary to incorporate a volatile rust inhibitor to prevent the rusting of the metal parts of the hydraulic system with which the fluid, in both liquid and vapor phases, came in contact. The class of antirust agents which is useful is the amine nitrites and amine carboxylates. These compounds are excellent two-phase rust inhibitors and are useful in amounts of from 0.05 to 1.0 (vol.) percent based on the oil phase of the emulsion. Examples of such compounds include Z-hydroxypropylamine nitrite, isopropylamine nitrite, cyclohexylamine nitrite, diisobutylamine nitrite, triethylamine nitrite, amylamine benzoate, diisopropylamine benzoate, monoethanolamine benzoate, isoamylamine salicylate, diisopropylamine butylphosphonate. The preferred rust inhibitor which is used in accordance with this invention is Z-hydroxypropylamine nitrite due to availability and cost. This compound has given excellent rust protection to metal parts of the hydraulic test systems in both the liquid and vapor phase despite the large amount of water present.

Other well known lubricant additives may also be advantageously included in the compositions of the present invention. For example, antiwear agents such as diand triphenyl phosphates, tricresyl phosphate, tributyl phosphate, triethyl phosphate, trioctyl phosphate and a mixture of monoand diethyl phosphoric acid esters wherein the alkyl group is a straight chain containing from 8 to 16 carbon atoms. These antiwear agents may be incorporated in amounts of up to 10 volume percent based on the mineral oil. The preferred antiwear agent on the basis of availability is tricresyl phosphate in an amount of from 0.5 to 10 percent by volume based on the mineral oil.

Examples of anti-oxidants which may be added to the emulsion of the present invention are hindered phenols such as 4-methyl-2,6-di-butylphenol, 2-t-butyl-4,6-dimethylphenol, 2,4,6-tributylphenol, 2,6-di-t-amyl-4-t-butylphenol, 2,4-di-methyl-o-propylphenol, t-butyl of o-secbutyl-p-cresol, t-butyl ether of o-sec-butyl-p-ethylphenol, t-amyl ether of o-sec-butyl-p-isobutylphenol, mixtures of oand p-polyalkylbenzylphenol, 1,1-bis(2-hydroxy-3-tbutyl-S-methylphenyl) ethane, 2,2-bis(2-hydroxy-3-t-butyl-S-methylphenyl) n-propane, 1,l-bis(2-hydroxy-3-5-dit-butylphenol) n-butane, 2,2-bis(2-hydroxy-3-t-butyl-5- methylphenyl)-2-tri-fluoroethane, and l,l-bis(2-hydroxy- 3-5-di-t-butylphenyl) methane.

These anti-oxidants may be incorporated in the oleaginous portion of the emulsion in an amount up to 1% by weight and preferably in an amount of about 0.3 weight percent. The preferred anti-oxidant is 4-methyl- 2,6-dibutylphenol on the basis of availability and cost.

In order to prevent unnecessary loss due to foam, it may be desirable to include an antifoam additive in the compositions of the present invention. Such antifoam additive is preferably a 10% solution of dimethyl silicone in kerosene which is added in an amount of about 150 parts per million to the oil phase of the emulsion.

A complete disclosure of all such additives that may be included in the fire resistant hydraulic fluid of the present invention is given in US. Patent 2,965,574.

I claim:

I. A fire resistant water-in-oil emulsion suitable for use as a hydraulic fluid consisting essentially of from 60 to 40 volume percent of water and from 40 to 60 volume percent of an oleaginous blend containing a major portion of a mineral oil having a viscosity in the range of from 50 to 300 SUS at F., from 1 to 12 volume percent of a lipophilic emulsifying agent selected from the group consisting a fatty acid partial esters of six carbon polyhydric alcohol monoand dianhydrides and about 0.05 to 2.50 volume percent of a hydrophilic emulsifying agent comprising an ethylene oxide-C to C alkylphenol adduct in a mol ratio of alkylphenol to ethylene oxide from 1 to to 1 to mols and a volatile corrosion inhibitor in an amount sufficient to inhibit corrosion in both the liquid and vapor phases.

2. A fire resistant water-in-oil emulsion suitable for use as a hydraulic fluid consisting essentially of from 60 to percent of water and from 40 to percent of an oleaginous blend containing a major portion of a mineral oil having a viscosity in the range of from 50 to 300 SUS at F., from about 2 to 6 volume percent of an oleic acid monoester of sorbitan, 0.1 to 1.0 volume percent of an emulsifying agent adduct having the formula:

@0 (cutout-ohm and a volatile corrosion inhibitor in an amount sufficient to inhibit corrosion in both the liquid and vapor phases.

3. A fire resistant Water-in-oil emulsion suitable for use as a hdraulic fluid comprising about 40 volume percent Water and about 50 volume percent of an oleaginous blend containing a major portion of a mineral oil having a viscosity in the range of about 50 to 100 SUS at 100 F, from about 2 to about 6 volume percent of an oleic acid monoester of sorbitan, 0.1 to 1.0 volume percent of an emulsifying agent adduct having the formula:

References Cited by the Examiner UNITED STATES PATENTS 2,965,574 12/1960 Tierney et al. 25278 3,050,465 8/1962 Francis 252-77 XR OTHER REFERENCES Surfonic Surface-active Agents, technical bulletin of the Jefferson Chemical C0,, Inc., 1958, pages 3 and 5.

JULIUS GREENWALD, Primary Examiner. 

3. A FIRE RESISTANT WAER-IN -OIL EMULSION SUITABLE FOR USE AS A HDRAULIC FLUID COMPRISING ABOUT 40 VOLUME PERCENT WATER AND ABOUT 50 VOLUME PERCENT OF AN OLEAGINOUS BLEND CONTAINING A MAJOR PORTION OF A MINERAL OIL HAVING A VISCOSITY IN THE RANGE OF ABOUT 50 TO 100 SUS AT 100*F., FROM ABOUT 2 TO ABOUT 6 VOLUME PERCENT OF AN OLEIC ACID MONOESTER OF SORBITAN, O.1 TO 1.0 VOLUME PERCENT OF AN EMULSIFYING AGENT ADDUCT HAVING THE FORMULA: 